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Propeller Singing

Propellers can sometimes produce a high-pitched singing noise. The causes of this phenomenon are not fully understood, but it seems to be related to factors like the number of propeller blades and differences between twin propellers. To mitigate singing, propeller designers have developed an "antisinging edge" which chamfers the trailing edge of blades on the suction side. This shape is intended to cleanly separate the water flow and avoid eddies that could cause vibrations and noise. While effective, thinning the edge too much could increase risks of erosion or fracture, so the antisinging edge should only be used as a last resort to minimize existing propeller singing.

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378 views1 page

Propeller Singing

Propellers can sometimes produce a high-pitched singing noise. The causes of this phenomenon are not fully understood, but it seems to be related to factors like the number of propeller blades and differences between twin propellers. To mitigate singing, propeller designers have developed an "antisinging edge" which chamfers the trailing edge of blades on the suction side. This shape is intended to cleanly separate the water flow and avoid eddies that could cause vibrations and noise. While effective, thinning the edge too much could increase risks of erosion or fracture, so the antisinging edge should only be used as a last resort to minimize existing propeller singing.

Uploaded by

Him Sati
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
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Download as DOC, PDF, TXT or read online on Scribd
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1Do Propellers Sing?

Yes, sometimes they sing: Some propellers in service produce a high-pitched noise, often referred to
as Singing. This sound typically is a clear harmonic tone much like a humming or ringing wine glass.
More of an annoyance than anything harmful, the causes of singing are not completely understood.
Many theories have been put forward to account for the phenomenon of Singing, but it appears to be
affected by critical factors for which the theories make no allowance. For instance, in some cases
when a twin-screw vessel has one propeller that sings, the noise is eliminated just by switching
position of propellers. Or had been replaced by an identical spare Propellers which were found
silent. Also the less number of blades the less cases of "singing".
Mitigation of Singing: Antisinging Edge
The singing is in function of propeller diameter and Rpm's, Boat speed and Trailing-edge size
(thickness) and roundness. In most of the cases not much can be done on Diameter, Rpm's or speed,
but we can modify the Edge Geometry. This has been the Strategy for all efforts to eliminate singing
Most Propeller professionals (and others) are familiar with the Antisinging Edge – a Chamfering of
the Trailing edge, typically on the Suction side. The intent of this shape is to avoid the creation of
curving flow eddies by cleanly separating the flow off of the blade.
The following graphic shows the Chamfering that goes from a 0.5 or 0.4 Radius to the tip of Suction
Side.

However the adoption of unduly thin edges can result in erosion or fracture of the blade near the
edges, it is advised that Antising Edge may be considered as a last resort to minimize the Singing of
an existing Propeller.

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